1. Field of the Invention
The present invention relates to an image projection display apparatus in which, from a luminance flux formed as a conglomerate of light of a plurality of wavelength bands, light of mutually different colors are separated out, each chromatic light being modulated so as to project an image onto a large screen.
2. Description of the Related Art
A projection-type image display apparatus has been developed in the past for displaying an image on a large screen, for use in outdoor displays in public places, or administrative displays, or in providing a display for high-resolution images.
Such projection-type display apparatuses can be generally classified as either transmission-type or reflection-type display apparatuses. In either case, light comprised of a conglomerate of a plurality of light wavelength bands is separated into light of mutually different wavelength bands and caused to illuminate an LCD (liquid-crystal display) panel, this incident light being modulated in pixel units according to a picture signal, so as to provide spatial modulation of the projected light.
There is a known LCD panel that makes use of three pixel electrodes corresponding to three primary colors as a unit, these being arranged in a matrix of liquid-crystal display elements in a single LCD panel, in what is known as a single-LCD projection display apparatus. A widely known single-LCD color projection display apparatus uses color-absorbing filters for the three primary colors red, green, and blue, disposed over the surface of pixel electrodes corresponding to these colors.
In an absorption-type color filter, however, although a particular wavelength is efficiently passed, light of other wavelengths is absorbed so that it is not passed. For this reason, in this type of display, there is the problem that light that passes through the color filter and reaches the pixel electrodes is reduced to ⅓ of the intensity of light (white light) that is incident to the absorption-type color filter.
A single-LCD color projection display apparatus to solve this problem was disclosed, for example, in Japanese Patent Application Laid-open Publication H4-60538. FIG. 1 is a plan view of a color projection display apparatus of the prior art, and FIG. 2 is a schematic representation of a liquid-crystal display device used therein.
In FIG. 1, white light w radiating from a light source 4 enters a collimator lens 5, and is converted to collimated light flux by the collimator lens 5. The collimated light flux is divided into light of three wavelength bands by a color separator 50.
The color separator 50 is made up of an R dichroic mirror 50R that selectively reflects only light r in the wavelength band of red light, and passes light of a different wavelength band, a G dichroic mirror 50G that selectively reflects only light g in the wavelength band of green light, and passes light of a different wavelength band, and a B dichroic mirror 50B that selectively reflects only light b in the wavelength band of blue light, and passes light of a different wavelength band. The dichroic mirrors 50R, 50G, and 50B are disposed at mutually different angles with respect to the axis of the collimated light flux.
That is, whereas the G dichroic mirror 50G is disposed at an angle of 45xc2x0 with respect to the optical axis, the R dichroic mirror 50R closer to the light source is disposed at an angle that is smaller than 45xc2x0, and the B dichroic mirror 50B is disposed at an angle that is greater than 45xc2x0. By means of these orientations, the red, green, and blue light beams each exit from the color separator 50 at different angles. For example, the red light r illuminates a micro-lens array 122 at an angle of incidence of +xcex1xc2x0, the green light g illuminates a micro lens array 122 at an incidence angle of 0xc2x0, and the blue light illuminates the micro-lens array 122 at the incident angle xe2x88x92xcex1xc2x0.
The color projection display apparatus has a liquid-crystal display 51. This liquid-crystal display 51, as shown in FIG. 2, has a microlens array 122 on a light entering side of the liquid crystal display element 123.
A liquid-crystal display element 123 is made up of glass substrates 125 and 129, between which are provided a signal electrode 126, a liquid-crystal layer 127, and a transparent electrode 128. The signal electrode 126 is made up of signal electrodes 126R, 126G, and 126B corresponding to the colors red, green, and blue, arranged in a stripe on the glass substrate 125 m above-described and the liquid-crystal layer 127 is provided on top of the signal electrodes. The transparent electrode 128 is provided between the liquid-crystal layer 127 and the glass substrate 129. It should be noted the alignment layer is not shown in FIG. 2.
The micro-lens array 122 is adhered to the upper surface of the glass substrate 129, and is formed by disposing in parallel vertical stripe lenticular lenses 122e each having a width that is the same as one group formed by a signal electrodes 126R, 126G, and 126B and corresponding to these colors of light.
The output light from a liquid-crystal display 51 like this is condensed by a condenser lens 54, and projected via a projection lens 52 in enlarged form as a color image on a screen 53.
In the above-noted image projection display apparatus of the prior art, because there is a requirement for high accuracy in the assembly angles of the dichroic mirrors 50R, 50G, and 50B, it is necessary to perform fine adjustment of the assembly angle at the time of assembly. FIG. 3 illustrates a method of adjusting the assembly angles of the dichroic mirrors 50R, 50G,and 50B. This drawing shows the case of adjusting the angle of incidence of the blue light b.
As shown in FIG. 3, of the light that enters the B dichroic mirror 50B, only blue light b is selectively reflected, so that it enters the micro-lens array 122 at point P at an incident angle of xe2x88x92xcex11. One method that can be envisioned of changing the angle of incidence is to rotate the B dichroic mirror 50B by xcex94xcex8 about the center point O, so as to reposition it at an angle shown by 50Bxe2x80x2. By doing this, the angle of incidence with respect to the micro-lens array 122 is corrected from xe2x88x92xcex11 to xe2x88x92xcex12.
With the above-noted method, however, although it is possible to correct the angle of incidence, there is an accompanying shift in the center position of incidence from point P to point Pxe2x80x2. If this kind of shift in center incidence position occurs and there is not a margin that will allow a shift in the illuminated light flux approximately the same as the surface area of the micro-lens array 122, there will occur a part of the light that will not enter the micro-lens array 122, to the extent of the shift that occurs, this causing the problem of a yellow line from which blue is absent at the edge of the projection screen 53, thereby causing a deterioration in the image quality. This occurs not just for blue light, but for red light as well.
A method that can be envisioned to prevent the occurrence of a shift in the position of incidence of light is to make the illuminated light flux diameter larger. If this is done, however, the efficiency of light usage worsens, and it is not possible to achieve a projection apparatus with high brightness.
With respect to the above problems, there is a method that is envisioned for preventing the occurrence of a shift in the center position of light incidence while adjusting the assembly angles of the dichroic mirrors 50R, 50G, and 50B. FIG. 4 shows a method of adjusting the angle of incidence of the illuminated light flux without changing the center position of incidence of the illuminated light flux.
In this method, after first translating the B dichroic mirror 50B rearward along the axis of incidence, the mirror is rotated by an angle of xcex94xcex8 about the center O of the dichroic mirror 50B. By doing this, it is possible to change the angle of incidence from xe2x88x92xcex11xc2x0 to xe2x88x92xcex12xc2x0 without changing the incidence position with respect to the micro-lens array 122.
However, in the above-noted method, in which the dichroic mirrors 50R, 50G, and 50B are rotated after translating them, it is necessary to have two mechanisms, one for translating the dichroic mirrors 50R, 50G, and 50B, and one for rotating the dichroic mirrors 50R, 50G, and 50B, thereby not only complicating the mechanism of the apparatus and increasing its cost, but also increasing the number of adjustment steps, thereby increasing the overall cost of manufacturing the image projection display apparatus.
Accordingly, it is an object of the present invention to provide an image projection display apparatus that enables adjustment of the three separated colors of light that are emitted, with a simple adjustment mechanism.
A first aspect of the present invention that solves the problems noted above in the related art is an image projection display apparatus in which, from light flux made up of a conglomeration of chromatic light of a plurality of wavelength bands, chromatic light having mutually different wavelength bands are separated, each of these chromatic light being modulated to project and display an image. This image projection display apparatus has a color-separation element formed by a plurality of wavelength-selective reflective mirrors that each selectively reflect light of a prescribed wavelength and pass light of a color having a different wavelength, these mirrors being arranged at a prescribed interval, and being oriented at a prescribed angle with respect to the optical axis of the light flux, a condensing element that condenses each of the chromatic light separated by the color-separating element, and an adjusting means for adjusting the spacing of each type of wavelength-selective reflective mirrors so as to changing the position of incidence of each separated chromatic light on the condensing element, thereby varying the angle of incidence of each of the colors of light exited from the condensing element,
According to the present invention as noted above, light flux containing a plurality of chromatic light is separated into separate chromatic light of different wavelength bands by a variety of wavelength-selective reflective mirrors. These separated colors of light are shifted in parallel from a main optical axis in accordance with the spacing of the wavelength-selective reflective mirrors, so that the various chromatic light are refracted by the condensing element in accordance with the amount of shift thereof. Therefore, the various chromatic light exited from the condensing element have an incident angle responsive to the amount of shift of each chromatic light with respect to the object being illuminated, and there is no change in the position of incidence thereof on the object being illuminated.
By causing the spacing between the various wavelength-selective reflective mirrors to change, it is possible to change the exit angle without causing a change in the position of incidence of the light exiting the condensing element with respect to the object being illuminated.
A second aspect of the present invention is an image projection display apparatus in which white light including three primary colors is separated into these colors, which are modulated to perform display and projection of an image. This image projection display apparatus has a color-separation element minimally having three V-shaped mirrors, a first V-shaped mirror, a second V-shaped mirror, and a third V-shaped mirror, made of a first wavelength-selective reflective mirror that, of the white light, reflects light of a first color and passes light of the second and third colors, and a second wavelength-selective reflective mirror, provided behind the first wavelength-selective reflective mirror, that selectively reflects light of a third color and passes light of the first and the second colors, these mirrors being joined at prescribed angle and sequentially arranged in a lamination direction, a condensing element that condenses light of the first color, the second color, and the third color separated by the color-separation element. In this image projection display apparatus, the white light is caused to enter the first wavelength-selective reflective mirror of the second V-shaped mirror, at which light of the first color is reflected and light of the second and third colors are passed. Then, after causing light of the first color to be reflected by the first wavelength-selective reflective mirror of the first V-shaped mirror, it is passed through the second wavelength-selective reflective mirror of the first V-shaped mirror, this light of the first color being exited from the first V-shaped mirror. Of the second and third color light passing through the first wavelength-selective reflective mirror of the second V-shaped mirror, the third color light is caused to be reflected by the second wavelength-selective reflective mirror of the second V-shaped mirror, the second color light is passed and the second color light exits from the second V-shaped mirror, third color light reflected by the second wavelength-selective reflective mirror of the second V-shaped mirror being caused to be reflected by the second wavelength-selective reflective mirror of the third V-shaped mirror, an the third color light exiting from the third V-shaped mirror.
In the above, the names first, second, and third are applied as a convenience in identifying the mutual positional relationship therebetween and, if there are three V-shaped mirrors, the center mirror is taken as the second V-shaped mirror, with the mirrors positioned to either side thereof being the first or the third V-shaped mirror. If there are four or more V-shaped mirrors, by selecting any mirror as the second V-shaped mirror, the names of the mirrors change. That is, in the case in which there are four or more mirrors, any mirror other than the mirrors at both ends is selected as the second V-shaped mirror, and the mirrors to either side thereof are taken as the first or the third V-shaped mirror.
According to the above-described second aspect of the present invention, white light containing a plurality of chromatic light enters a central second V-shaped mirror, the result being that the white light is separated into chromatic light of different wavelength bands by the second V-shaped mirror and the first and third V-shaped mirrors disposed to either side thereof.
Because the separated light of each color is shifted in parallel from the main optical axis by a distance responsive to the spacing between the V-shaped mirrors, the light beams of each color are refracted by the condensing element by an angle amount that is responsive to the amount of shift thereof. Therefore, each color light exiting the condensing element has an angle of incidence responsive to the amount of shift thereof with respect to the object to be illuminated, and there is no change in the position of incidence at the surface of the object being illuminated.
A third aspect of the present invention is a variation of the second aspect of the present invention, wherein the spacing between the plurality of V-shaped mirrors is adjusted in the lamination direction, so that the positions of incidence of the first color light, the second color light, and the third color light separated by the color-separation element are changed, thereby enabling a change in the angle of exit of each color from the condensing element.
According to the above-noted third aspect of the present invention, by changing the spacing between the various types of V-shaped mirrors in the lamination direction, it is possible to change the angle of exit without changing the position of incidence with respect to the object being illuminated.
A fourth aspect of the present invention is a variation on the first aspect of the present invention, wherein, of the wavelength-selective reflective mirrors, one wavelength-selective reflective mirror has a dimension that is smaller than the others.
According to the above-noted fourth aspect of the present invention, by reducing the amount of reflection of one of the colors of light, it is possible to adjust the color balance or contrast. In particular when separating colors using a color-separation element, because there is a tendency for the intensity of light of a color that is not shifted from the optical axis of the illuminating light to be larger than light of the other shifted colors, this arrangement enables the reduction of the amount of reflection of that color, thereby enabling adjustment of balance with respect to the other colors.
A fifth aspect of the present invention is an image projection display apparatus in which a light modulation section is illuminated by light flux radiated from a light source, and is thereby modulated, so as to project an image. This display apparatus has an integrator that has a large number of small-diameter lenses which convert the light flux from the light source to a large number of light fluxes, a first image optical system for overlapping this large number of light fluxes at a first image plane, and a second image optical system for forming the image formed at the first image plane as at a second image plane, wherein a virtual image plane with respect to the color-separation element of the first image plane, a principal plane of the second image optical system, and the light modulation section are disposed so as to intersect at a substantially straight lines that are extension lines thereof.
According to the fifth aspect of the present invention, by converting a light flux from a light source into a large number of light fluxes, grouping these first at a first image plane using a first image optical system, and then forming an image at an illuminated plane of the light modulator section, which is the second image plane, it is possible to illuminate the light modulation section with a uniform illumination. When this is done, the second image optical system and the light modulation section receiving plane, which is the second image plane form a perspective optical system, it is possible to prevent the occurrence of defocusing in the region of the edge of the illuminated light flux.